The Tianjin explosion and the scaling laws of nuclear weapons

Chew

Senior Member.
Some commentators have claimed the Tianjin explosion was caused by a tactical nuke. However this does not fit with the known scaling laws of the effects of nuclear weapons. They seem to think a small nuke is exactly like a big nuke, only smaller and cuter.

Glasstone and Dolan (1977) wrote the definitive work on the effects of nuclear weapons and I cite their work throughout.

The blast radius increases with the cube root of the yield. The prompt ionizing radiation radius increases to the 0.19 power of the yield. The radius of the fireball of a surface burst increases to the 0.4 power of the yield. The time after detonation of the peak of the thermal radiation output increases to the 0.44 power of the yield. And the duration of the fireball is 10 times the time of the peak thermal output. That means if you time the duration of the fireball you can calculate the yield. This compilation video of the explosion includes a security cam with a timestamp.


The fireball lasts for 22 seconds so the peak thermal power occurred at 2.2 seconds after detonation. Plug in the numbers for the time of peak thermal radiation output and it comes up with a yield of 8.2 megatons!!!

http://www.fourmilab.ch/etexts/www/effects/eonw_7.pdf#page=35

Another way to estimate yield is to measure the radius of the fireball. thunderf00t did that in this video and came up with a radius of 75 meters:


Section 2.127 describes the scaling and constants of the radius of the fireball:

http://www.fourmilab.ch/etexts/www/effects/eonw_2.pdf#page=45

For a surface burst that radius would indicate a yield of 0.66 kilotons. But that yield would give a fireball duration of 0.34 seconds.

Since two extremely well-studied phenomena of nuclear weapons give incredibly huge discrepancies in yield (8200 and 0.66 kilotons), and the observed fireball radius and fireball duration are mutually exclusive, it is very safe to say this explosion came no where near to obeying the scaling laws of nuclear weapons and therefore it was not caused by a nuclear weapon.
 

Whitebeard

Senior Member.
Comparing the damage of the Tianjin blast to some other powerful explosions shows similar effects.

First up the Flixborough disaster of 1974
30ddb1070d6d94295d26ada3d2d5f07a.jpg
and there are reports of some parts of the plant being found 12 miles away.
from: http://www.hulldailymail.co.uk/Flix...tory-21169337-detail/story.html#ixzz3k7ZKUFFu

Second up the Soham explosion from 1944
e8f7866d37ca7ef3ed07e3663c032642.jpg
Although a lot smaller than the above blast, it was a railway wagon loaded with bombs, it still created a large crater and had a devastating blast.
and finally something far more recent... the Buncefield fire and explosion
de981e244eef6e3bae2cce0fc0c3bda9.jpeg
I live 110 miles from Buncefield and I heard it!!

Have a read of the reports, the effects of all three blasts (and these are just the three that sprang to mind, there are many others) do not differ in effect and result from the Tianjin blast (apart from variations in scale)

Bottom line is you don't need a nuke to make a large and very devastating bang, petrol chemicals and hydro-carbons are more than capable of doing that all by themselves give enough of them and an ignition source.
 
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BombDr

Senior Member.
They seem to think a small nuke is exactly like a big nuke, only smaller and cuter.


This is not the first time the ill-informed have claimed any large explosion is a 'tactical nuke', 'mini nuke' or even 'neutron bomb' on the basis of a fireball and mushroom cloud:




What they fail to notice is the lack of blinding flash, the cameraman remaining alive to film the scene and the total and utter lack of any increased radiological activity of any sort.

But it must be true, because they saw it on the internet....
 

JRBids

Senior Member.
They only believe what they see with their own eyes, and most importantly: that is what they WANT it to be.
 

drut

Member
I linked to it previously but it got lost in the shuffle:

So the quote is in 7.86:

Where did you the idea you can use the fireball duration to estimate tmax? Is it in the book?

Have you tried using this method on known nuke videos of known yield?
 

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